Process for wet spinning and washing synthetic fibers



y 9, 1961 G. w. STANTQN 2,983,571

PROCESS FOR WET SPINNING AND WASHING SYNTHETIC FIBERS Filed April 23,1958 2 Sheets-Sheet 1i Fresh wo/er in /e a (1/ I I 14 .1 5 45, 75

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George 11/ 8/0/7/0/7 May 9, 1961 G. w. STANTON PROCESS FOR WET SPINNINGAND WASHING SYNTHETIC FIBERS Filed April 25, 1958 2 Sheets-Sheet 2INVENTOR. Geo/9E 14 S/an/ofl HTTORNfY United States Patent Of ice TheDow Chemical Company, Midland, Mich, a corporation of Delaware Fae-aApr. 23, 1958, Ser. No. 730,315 7 Claims. (31. 18-54) The presentinvention resides in the field of synthetic textile fibersandcontributes tothe art of their manufacture. ,More precisely, it relatesto a useful and advantageous process for the simultaneous and continuouswet spinning and washing of man-made fibers that are prepared by beingcoagulated from suitable spinning solutions or equivalent compositions(such as spinnable dispersions inaqueous coagulating spin baths andsubsequently washed with water to remove residual spinning solutionsolvent from the freshly wet spun fiber. The in,- ventionhas particularreference to the manufactured acrylonitrile polymer fibers which arefabricated from fiber-forming acrylonitn'le polymers that contain in thepolymers molecule at least about 80 Weight percent of acrylonitrile,especially polyacrylonitrile, which are wet spun in and with systemsthat are adapted to utilize aqueous coagulating liquids for the spinningoperation, such as systems wherein ethylene glycol, dimethyl formarnide,dimethyl sulfoxide, butyrolacetone and the like or the various aqueoussaline polyacrylonitrile-dissolving solvents are employed as spinningsolution solvents forthe polymer and are also present innon-polymer-dissolving quantities in the aqueous coagulating liquid usedin the spin bath. The utile, known aqueous saline solvents for thevarious fiber-forming acrylonitrile polymers and polyacrylonitrile,include zinc chloride, the various thiocyanates such as calcium, lithiumbromide, salt mixtures of the, so-called flyotropic series, and othersrecognized by the art, as has been disclosed, among other places, inUnited States Letters Patents Nos. 2,140,921; 2,425,192; 2,648,592;2,648,593; 2,648,646; 2,648,648; and 2,648,649. Advantageously, aqueouszincchloride solutions are used forthe purpose. I I It isthe majorobject of the present invention to providean improved process for thecontinuous wet spinning and simultaneous washing of various syntheticpolymer fibers, particularly acrylonitrile polymer fibers, wherein thespinning, coagulation and complete water washing of the fibers isadvantageously accomplished in continuous se'quencein the same unitaryprocessing operation in and with the same, unitary, integralmanufacturing apparatus. A particular object of the invention is toprovide a process of' the indicated type and nature that would bepeculiar'ly well adapted for utilization for and in the preparation ofacrylonitrile polymer fibers, yarn, threads, tow bundles and the likeand related filamentary products using the highly advantageous saltspinning techniques with aqueous systems, such as those that employaqueous solutions of zinc chloride or its saline equivalents fordissolution of the polymer into a spinning solution and forconstitution, in ,non-polymer-dissolving quantities, of the coagulatingspin bath. i i These objects and cognate benefits and advantages ma beachieved readily in the practice of the present invention whose process,in continuous and uninterpretedsequence,,comprises and entails extrudingor spinning into filamentaryor- (the like form a spinning solution of asyniiber-formingpolymer dissolved in a watermiscible Patented May 9,1961 solvent for said polymer, said spinning solutionibeing adapted tobe coagulated in an aqueous solution of said solvent ofnon-polymer-dissolving concentration, said spinning solution beingextruded through a suitable spinnerette or other extruding device intothe spinning end or zone of a chamber that is comprised of a spinningend or zone and a withdrawing end or zone and having a plurality ofseparate, intercommunicating liquid recirculating zones between saidspinning end and said withdrawing end; said chamber being filled with anaqueous liquid of gradient increasing concentration from that ofsubstantially pure water in said withdrawing end of said chamber tothat, in said spinning end of said chamber, of a non-polymer-dissolvingaqueous coagulating solution of said solvent constituent with respect toits dissolved concentration of said solvent constituent from saidspinning solution; coagulating said freshly wet spun filaments of saidspinning solution in said non-polymer-dissolving or coagulating solutionportion of saidliquid in said spinning zone insaid chamber; passing saidfreshly wet spun and coagulated filaments through aqueous liquid insequence from said spinning zone through said intercommunicat ing,liquid recirculating zones in said chamber to said withdrawing end orzone of said chamber; admitting substantially pure water in saidwithdrawingend or zone of said chamber and passing it countercu'rrent tosaid fila-' ments in said chamber at such a rate and in such quanti}ties with respect to such extrusion of spinning solution thattheconcentration of polymer solventin said non polymer-dissolvingaqueous solution of said solvent in said portion of said liquid in saidspinning zone of said chamber is maintained at an efiicient andeffective coagulating concentration for said spinning solution;withdrawing liquid from said withdrawing zone of said chamber at aboutthe same volumetric rate as it is applied to said chamber in the form ofsaid water admitted to said withdrawing zone and the liquid extrudedwith said spinning solution less the quantity of liquid removed fromsaid chamber with said filaments; recirculating said aqueous liquid ineach of said recirculating zones substantially transversely through andabout said freshly Wet spun filaments passing therethrough so as toextract and remove residual spinning solution solvent therefrom; andwithdrawing said freshly wet spun and washed filaments from saidwithdrawing zone in said chamber. i

Further features and advantages of the invention will be manifest in thefollowing description and specification, taken in connection with theaccompanying drawing, which schematically illustrates the invention inseveral views, wherein:

Figure 1 is a simplified cross-sectional elevation which represents anapparatus that is adapted to perform the present process and whereinsaid process is being-conducted;

Figure 2 is a fragmentary, schematic,cross-sectional elevation of partof another suitable apparatus for practice of the invention whichillustrates a modified arrange ment of the liquid recirculating means inoneof the re:

circulating zones; and

Figures 3 and 4 are schematic cross-sectional plan views that depictsuitable structural configurations of the chamber and furtherrespectively illustrate theliquid recirculating means in Figures 1 and2.

In order to successfully practice the invention, a unitary, integralcontainer or chamber is required having a spinning end or zone at one ofits extremitiesand a withdrawing end or zone at its opposite extremity,said spinning and withdrawing zones being separated in said chamber by aplurality of liquid recirculating zones or sections which are so formedand disposed as to permit liquid communication between .said spinningand withdrawing zonesand to allow travel or progression of filamentarymaterial through the chamber. Such an installation is indicatedgenerally by the reference letter C in the several figures of theaccompanying drawing. With predominant reference to Figure l, thechamber C has'a spinning zone or end A at one of its extremities and awithdrawing end' or zone Z at the opposite extremity. A plurality ofrecirculating zones O are dis posed between the spinning zone A and thewithdrawing zone Z of said chamber. Each of the recirculating zones arebounded and defined by spaced baflie plates B. Each of the bafiles B'hasa uniform and respectively similar central opening H therein to permitcommunication through the plurality of installed bafiles from thespinning zone to the withdrawing zone of said chamber and to provide foruninterrupted passage of filaments through the apparatus. V

The chamber C may have any desired configuration and be of anysuitable'physical dimensions so as to be adapted for the intendedmanufacturing purpose. The baffles B are of such construction as to fitwithin the chamber and to provide the central aligned openings H. Thusas shown in Figure 3, the chamber C may have a cylindrical configurationwith theinterfitting bafiles B being of annular design. Or, as shown inFigure 4, a generally rectangular chamber may be utilized with suitable,centrally open, accommodating bafiies. Of course, as will be appreciatedby those with the skill of their calling, many other equivalent andsatisfactory designs are possible. The central openings H in the bafileB must, of course, be sufficiently large to permit ready passage of thefreshly wet spun filaments through the length of the chamber and thegenerally countercurrent movement of the liquid through the chamberagainst the path of travel of the filaments from the withdrawing zone tothe spinning zone of said chamber. The openings H themselves maybe'shaped in any manner to best accommodate with suitably close spacingthe filamentary bundle being handled. Thus, generally round or rope liketow bundles are ordinarily better handled through round openings H, asillustrated in Figure 3. Tow bundles having a relatively fiat and wide,ribbon-like assembly are usually better passed through matchingrectangular openings H, as in Figure 4. As will be readily apparent, theopenings H in the baflies B should not be so large asto interfere withefiicient internal recirculation ofthe liquid in each of the recirclingzones in said chamber or to prevent a thorough flushing and treatingaction of the counter-current flowing liquid on the freshly wet spunfilaments during their passage through the chamber. Suitable dimensions.in particular instances can be readily designed by elementaryinvestigation and application of known principles.

A spinning solution or other spinnable dispersion of fiber-formingmaterial of the indicated variety is provided under an extrusionpressure (developed by any suitable means not shown) in a conduit ormass tube M, upon which is mounted the spin head S. The spin head S maybe comprised of a conventional spinnerette (or a plural bank of same).for the extrusion of filamentary materials or any other desiredextrusion device, such as multiple orifice die or the like, adapted forthe spinning of liquid coagulable fiber-forming compositions intodesired filamentary products. If desired, of course, the

invention may be practiced so as to prepare monofilamerits in eachapparatus installation by utilizing a single orifice spinnerette or diefor the spin head. It is ordinarily, a decided advantage, however, forthe spinning solution to be directly. spun through multiple orificespinnerettes or the like extrusion devices which are adapted tosimultaneously prepare a plurality of filaments so as to directly formmultiple filament strands to tow bundles. of considerable magnitude,such as those comprised of at least about 3,000 individual filaments ofthe desired size. Oftentimes, large tow bundles may comprise as many as10,000 or 50,000 to 200,000 or more individual filaments. As'indicated,the tow bundle 4 a, can be assembled and handled so as tohaveranydesired cross-sectional patterns.

Upon its extrusion, the spinning solution is coagulated into thefilaments F by the action and effect of the nonpolymer-dissolvingaqueous coagulating solution of the portion of the liquid L in said spinzone which contains the maximum concentration in said liquid of thesolvent constituent from said spinning solution. The freshly wet spunfilaments are passed in tow bundle or other desired form from thespinning zone A of the chamber C through the recirculating zones 0of-the chamber to the withdrawing zone Z, from which they are withdrawnby means of a suitable pair of towbighting nip or withdrawing rolls R orother equivalent tow withdrawing or forwarding means (including variousthread advancing devices) that may be desired. During their travelthrough the chamber (which maybe heatedor cooled, or both, along itslength in any desired or necessary manner), the freshly wet spunfilaments are passed through the countercurrent flow of aqueous liquid Lin' the chamber until they are subjected to substantially pure water inthe withdrawing zone Z. The water is admitted to zone Z through thefresh water inlet-I by; any suitable means, such as ametering pump, notshown; This accomplishes a thorough and final washing and extraction ofresidual solvent from the spinning-sol d tion that obtains in thefreshly wet spun fibers. I-f 'cool fresh water isdesired in the processit may also be ad vantageous to employ a suitablecooling means (likewisenot shown) in operative association with theinlet I to permitsatisfactory regulation and control of theeteme perature of the waterbeing admitted. v a

The liquid L in each of the recirculating zones O'be tween the spinningzone A and the withdrawing zone Z of the chamber is recirculated duringits generally countercurrent passage through the length of the chamberwithin each of the zones 0 by any suitable means adapted to locally passthe portion of liquid in the individual're' circulating zonesubstantially transversely through and between the freshly wet spunfilaments which are passing through each of the recirculating zones 0 intheir travel through the chamber. Advantageously, the recir culatingmeans for the liquid in each of the recirculating zones 0 may be a pumpmeans P which withdraws' liquid from each of the recirculating zonesthrough the recirculating tube outlet W and readmits it in a pathgenerally-transverse to the filaments through the recirculatingtube'inlet X. Of course, more than one liquid 'r'ecirculating' means orpump maybe utilized ineach recirculating "zone oand the recirculatingtube outlets and inlets W and X, respectively, can be disposed atopposite sides from one another in the chamber or in other arrangements.They-need not be in communication with the recirculating zone'atsubstantially the same point therein, despite the fact that they are soshown in Figure 1 of the drawing. Figures 2 and 4 of the drawingillustrate one of the indicated suitable variations in which therecirculating tube outletsand inlets are on opposite sides of arectangular chamber. Frequently, such an arrangement may be beneficialto accomplish 'a more positive through-flushing action onthe'filamerits. In addition, the recirculating tube inlets X may bearranged and adapted toexpel therecirculated liquid at a pointimmediately adjacent to the filaments'bein'g it is withdrawn through theoutlet tube Valong with additional liquid introduced in said spinningsolution and not carried out with the filaments withdrawn from thewithdrawing zone. A pump or other liquid withdrawing means (not shown inthe drawing) may be employed in aces-n conjunction with the outlet tubeV. During its counter.- current passage through the chamber, theconcentration of spinning solution solvent in the liquid L graduallyincreases. This, as is apparent, is by virtue of the extracting andwashing efiect of the aqueous liquid on the watermiscible spinningsolvent being removed'from the freshly wet spun filaments. Such action,of course, results in the final washing of the filaments prior to theirwithdrawal from the withdrawal zone Z of the chamber and provides thenon-polymer-dissolving, aqueous coagulating solution of said solventconstituent of the portion of the liquid L whichoccurs in the spinningzone Z of the chamber.

As will be appreciated by those who are skilled in the art, the volumeof substantially pure water to be admitted in the withdrawing zone I ofthe chamber must be correlated to the requirements of the wet spinningsolvent desired for coagulation in the portion of the liquid in thespinning zone A of the chamber. Of course, the volumetric requirement ofsubstantially pure water for efiicient washing of the freshly wet spunfilaments must also be met. In the usual case, however, the quantity ofwater required to continuously dilute the solvent from the spinningsolution to a dissolving coagulated concentration is at least ample forpurposes of thoroughly washing the freshly wet spun filaments,particularly when the chamber C is provided with an adequate length andhas a satisfactory and eificacious number of recirculating zones 0interdisposed between the spinning zone A and the withdrawing zone Z. 1

. In many cases, it is most desirable, as implied in the drawing, topractice the invention with the apparatus in vertical dispositionwiththe spinning and filament progression being in a generally upwarddirection. This simplifies handling of the liquid through the zones bytaking advantage of gravity flow. Of course, the spinning may also bedownward using pumps to effect progress of the liquid through the zones.Horizontally and otherwise disposed units may also be employed. fAftertheir extrusion, coagulation, washing and-withdrawal from the liquid inthe chamber, the freshly vwet spun filaments may be subsequently handledand treated in any desired or necessarymanner for purposes of convertingthem to a finished fiber product. Thus, they may be stretched orotherwise treated for purpose. of heat treating or relaxing the fibersin any desired way or they may be subjected to additional treatments ofany appropriate nature, including application of finishes, lubricantsand the like. or imposition of crimp prior to being dried and finallycollected as completely manufactured products.

I As has been indicated, when acrylonitrile polymer, particularlypolyacrylonitrile, fibers are being manufactured, zinc chloride may mostadvantageously be utilized as the sole, or at least the principal,saline solute in the spinning solvent employed for the polymer. In suchinstances, the aqueous solution of zinc chloride in the spinningsolution may advantageouslybe in a concentration of from 55. to 65,preferably about 60 percent by weight, based on the weight of theaqueous solution. The quantity of sub.- stantially pure water passedcountercurrent tothe filaments in the chamber should be sufficient, whensuch aqueous zinc chloride solvent spinning solutions are em ployed, soas to maintain the concentration of zinc chloride in the portion of theliquid in the spinning zone at a non-polymer-dissolving coagulatingconcentration of at least about percent-by weight; advantageously frornabout to 50 percent by weight, and preferably between about and percentby Weight. In such aqueous zinc chloride systems for acrylonitrilepolymers, wherein the freshly wet spun polymer is generally obtained inan aquagel form, it is generally desirable for the spinning solutionthat is extruded to contain between about 4 and 20 percent by weight ofdissolved polymer; more advantageously from about 6 to 15 percent byweight of dissolved polymer; and preferably,particularly when.polyacrylonitrile fibers are being manufactured, from about 8.5 to 11.5percent by weight of fiber-formingpolymeric solids in the spinningsolution. I 1

Aqueous zince chloride spinning solutions of fiberforming acrylonitrilepolymers are beneficially extruded at a spinning temperature of from Oto 50 C.; preferably from about l0to 30C., into an aqueous zinc chloridecoagulating liquid that is maintained at a coagulating temperature offrom 0 to 30 C.; preferably from about 10 to 20 C. Under the indicatedconditions, the amount of fresh water that is required to effect a suitable coagulating atmosphere in the portion of. .the liquid in thespinning zone A can be determined by simple material balance, takinginto account the quantity per unit time of spinning solution beingextruded and the amount of water being withdrawn from the liquid. byentrapment and entrainment in the freshly wet spun and washed aquagelfibers. Thoroughly washed acrylonitrile polymer aquagel fibers,incidentally, are usually found to contain not more than 5 /2 parts byweight of water (including residual extrinsic or exterior waterassociated therewith) for each part by weight of dry polymer there in.More frequently, washed acrylonitrile polymer aquagel fibers are foundto contain from about 2 and usually from about 3 to 4 parts by weight ofwater for each part by weight of polymer. I

When practicing the present invention, it is usually advantageous toemploy an apparatus having at least about four to six or even at leasteight recirculating zones between the spinning and withdrawing zones inthechamher and for each of the recirculating zones to be about of equalphysical proportions. In general, as will be appreciated by artisansversed in the premises, the 'total number of recirculating zonesnecessary will be in inverse-proportion to the fiber flushing or washingefficiency ineach zone. Better and more thorough circulation .(withinthe limits imposed by safe handling of the freshly extruded andcharacteristically physically tender and sus? ceptible to damage fibers)of the liquid in each zone diminishes requirements for total numbers ofindividual zones. In such apparatus it is desirable for the spinningzone to comprise not more than about 20 percent of the total length ofthe chamber and for the withdrawing zone to have about the samedimensions as each ofthe recirculating zones employed. It is generallyadvantageous for the chamber. that is utilized to have a length of atleast about ,15 and preferably at least about 30 feet. In the operationof the process, it is beneficial and most practical to recirculate theliquid in each of the recirculating zones at such a rate that at leastabout 15 parts by volume of liquid are recirculated through and betweenthe filaments or fibers being passed through the zone for each part byvolume of liquid progressing through the zone inits generallycountercurrent passage through the chamber. More advantageously, atleast about 20 parts by volume, and preferably at least about .30 partsby volume, of the liquid in each zone is recirculated'for eachpartbyvolume of liquid passing countercurrently through the chamber.

The invention is further manifest in and by the following docentexamples.

' Example I A process and apparatus similar to that represented inFigure 1 (and 3) of the accompanying drawing is utilized for themanufacture of synthetic polyacrylonitrile fibers. The verticallydisposed chamber C iscylindrical in, configuration. and has an internaldiameterof about /2 foot with a liquid-containing internal length ofabout 34 feet. It is separated into 15 recirculating zones by a total'of16 annular bafiies, each having round, central openings of about inch indiameter. The baffies are provided atuniformly spaced intervals in thechamber of about 2 feet, with the length of the spinning zone A beingabout 3 feet. A single multiple orifice spinnerette 7 having. a total ofabout three thousand individual round jet hoIesofIS rnil diameterieachis utilized asa spin head. and is situate in the spinning zone at thebottom of thechamber.

' The spinning solution extrude is comprised of polyacrylonitrile havingan average molecular weight between about'SO and 35 thousand dissolvedin an aqueous 60 percent" by weight solution of zinc chloride. Thespinningsolution has a total polymer solids content of about 10 percentby weight,based on the weight of the solution. All of the spinningsolution is continuously extruded upwardly through the spin head at atemperature of about 25 C. and under a rate, of extrusion of about 60pounds per'hour so as to be coagulated in the form of aquagel filamentsat a continuous linear rate of about 12.5 feet per minute by the actionof the aqueous, nonpolymer-dissolving solution ofzinc chloride in theliquid in the lowermost spinning zone portion of the chamber. Thefreshly wet spun filaments are formed and handled in the" form of agenerally round, relatively rope-like tow bundle.

The zinc chloride concentration of the coagulating liquid in thespinning zone portion is maintained at about 44 percent by weight, andis held at an average temperature'of'about 15 C." during the spinningoperation. A cooling jacket is employed about the spinning zone toassist in" temperature regulation. About 43 pounds per hour of freshwater,at a temperature of about 20 C., is introduced through the inlet Iin the withdrawing zone of the chamber and is continuously passedcountercurrentto the filaments therein In each of the recircu latingzones the liquid is recirculated substantially transversely through thefilaments at a rate of about 30 parts by volume of recirculating liquidfor each part by volume of liquid being introduced as fresh water in thewithdrawing zone of the chamber. The recirculation of liquid in eachof'the recirculating zones is accompaniedby means of recirculating pumpsof sufiicient capacity for the purpose and connected (as shown inFigures 1 and 3 of the drawing) through inlet and outlet tubesforhandling the recirculatedliquid. About 73 p'oun'dsper hour of a 44percent by weight aqueous solution of zinc chloride is withdrawn fromthe coagulating liquid outlet V from the spinning zone A of the chamber.The aquagel filaments are withdrawn from the uppermostzone Z of thechamber in a thoroughly'washed condition in which they contain onlyabout 0.1 percent by weight of salt (including the salt in the residualliquid adhering thereto), based on the weight of the polyacrylonitriletherein, and about 4 parts by weight of water for each part by weight ofdry polymer therein. After being withdrawn from the chamber, the fibersare oriented by stretching in hot water to a total of 12 times their wetspun, unstretched length. They are then dried for 20 minutes in hot airat 150 C.

By the foregoing procedure, there is continuously producedpremimur'nquality, 3 denier per filament polyacrylonitrile fibers havinga tensile strength in the neighborhood of 4 grams per denier, anelongation in the neighborhood of 30 percent and a wet yield strength ofabout 1 gram per denier, The product fibers are colorless and, uponimmersion in boiling water, experience less than 1 percent shrinkage.

Example II gular openings of about A x 2 /2 inches to pass the flat tow'bundle through the zones. The liquid is recirculated through thefilaments in each zone using a single pump for each'zone with the inletand outlet tubes in opposite sides of the zone across the tow, asdepicted in Figure 4 of the drawing; Commensurate excellent results areobtained. 7

Excellent results are also realized when the forgoing procedure isfollowed to wet spin acrylonitrile and other fiber-forming polymersusing other solvent and aqueous coagulating systems therefor; Thepresent invention is intended to be gauged in its interpretation in thelight of the hereto appended claims without unnecessary limitation to orby the foregoing demonstrative specification and description. i What isclaimed is: 1. Method for continuously wet spinning and washingsynthetic textile fibers which comprises forming a watercoagulablespinning solution of a synthetic fiber-forming polymer in a watermiscible solvent for said'polyme'r extruding said spinning solutionthrough a filament shaping device into the spinning zone of an elongatechamber having a spinning zone and a withdrawing zone and a plurality ofseparate, intercommunicating liquid recit culating zones therebetween;maintaining said chamber full of an aqueous liquid of gradientincreasing 00116611? tration from that of substantially pure water insaid withdrawing zone to that, in said spinning zone, of an aqueouscoagulating solution of said solvent for said spinning solu tion;coagulating said freshly wet spun filaments of said spinning solution infilamentary form in said coagulating solution portion of said liquid insaid spinning zone; pass ing said freshly wet spun and coagulatedfilaments from said spinning zone through said intercommu'nic'ating,liquid recirculating zones'in said chamber to said with drawing zone;admitting substantially pure water in said withdrawing zone of saidchamber and passing it countercurrent to said filaments in said chamberat a rate that is adapted to maintain the water concentration in saidaqueous coagulating solution in said spinning zone at a coagulatingconcentration for said spinning solution; passing aqueous liquid fromsaid withdrawing zone of said chamber internally to said spinning zoneof the chamber at about the same volumetric rate as it is suppliedthereto; recirculating said aqueous liquid being passed internally insaid chamber in each of saidrecirculating zones substantiallytransversely through and about said freshly wet spun filaments passingtherethrough; and withdrawing said freshly wet spun and washed filamentsfrom said withdrawing zone in said chamber.

2. The method of claim 1, wherein said filamentary material is passedthrough at least about 8 recirculating zones between said spinning zoneand said withdrawing zone.

3. The method of claim 1, wherein at least about 15 parts by volume ofliquid are continuously recirculated within each of the recirculatingzone through and between the filaments being passed through each zonefor each part by volume of liquid progressing in a generallycountercurrent manner to said filaments through each of said zones.

4. The method of claim 1, wherein said spinningsolution is comprised ofa fiber-forming acrylonitrile polymer containing in the polymer moleculeat least about percent by weight of acrylonitrile dissolved in a watermiscible solvent therefor.

5. A method in accordance with the method set forth in claim 4, whereinsaid solvent is an aqueous polyacrylonitrile-dissolving saline solution.a

6. A method in accordance with the method set forth in claim 5, whereinsaid aqueous saline solution is a solution of zinc chloride in waterthat contains from 55 to 65 percent by weight of dissolved zincchloride, based on the weight of the solution. 1 a i 7. The method ofclaim 1, wherein said spinning solution is extruded and said freshly wetspun filaments are handled and passed through said chamber in agenerally vertically upward direction.

References Cited in the file of this patent UNITED STATES PATENTS2,094,099 Dreyfus Sept. 28, 1937 Roberts Jan. 2, 1951 Hoxie Sept. 30,1952 Stanton Apr. 30, 1957 FOREIGN PATENTS Germany Sept. 15, 1932 GreatBritain July 1, 1928

1. METHOD FOR CONTINUOUSLY WET SPINNING AND WASHING SYNTHETIC TEXTILEFIBERS WHICH COMPRISES FORMING A WATERCOAGULABLE SPINNING SOLUTION OF ASYNTHETIC FIBER-FORMING POLYMER IN A WATER MISCIBLE SOLVENT FOR SAIDPOLYMER EXTRUDING SAID SPINNING SOLUTION THROUGH A FILAMENT SHAPINGDEVICE INTO THE SPINNING ZONE OF AN ELONGATE CHAMBER HAVING A SPINNINGZONE AND A WITHDRAWING ZONE AND A PLURALITY OF SEPARATE,INTERCOMMUNICATING LIQUID RECIRCULATING ZONES THEREBETWEEN, MAINTAININGSAID CHAMBER FULL OF AN AQUEOUS LIQUID OF GRADIENT INCREASINGCONCENTRATION FROM THAT OF SUBSTANTIALLY PURE WATER IN SAID WITHDRAWINGZONE TO THAT, IN SAID, SPINNING ZONE, OF AN AQUEOUS COAGULATING SOLUTIONOF SAID SOLVENT FOR SAID SPINNING SOLUTION, COAGULATING SAID FRESHLY WETSPUN FILAMENTS OF SAID SPINNING SOLUTION IN FILAMENTARY FORM IN SAIDCOAGULATING SOLUTION PORTION OF SAID LIQUID IN SAID SPINNING ZONE,PASSING SAID FRESHLY WET SPUN AND COAGULATED FILAMENTS FROM SAIDSPINNING ZONE THROUGH SAID INTERCOMMUNICATING, LIQUID RECIRCULATINGZONES IN SAID CHAMBER TO SAID WITHDRAWING ZONE, ADMITTING SUBSTANTIALLYPURE WATER IN SAID WITHDRAWING ZONE OF SAID CHAMBER AND PASSING ITCOUNTERCURRENT TO SAID FILAMENTS IN SAID CHAMBER AT A RATE THAT ISADAPTED TO MAINTAIN THE WATER CONCENTRATION IN SAID AQUEOUS COAGULATINGSOLUTION IN SAID SPINNING ZONE AT A COAGULATING CONCENTRATION FOR SAIDSPINNING SOLUTION, PASSING AQUEOUS LIQUID FROM SAID WITHDRAWING ZONE OFSAID CHAMBER INTERNALLY TO SAID SPINNING ZONE OF THE CHAMBER AT ABOUTTHE SAME VOLUMETRIC RATE AS IT IS SUPPLIED THERETO, RECIRCULATING SAIDAQUEOUS LIQUID BEING PASSED INTERNALLY IN SAID CHAMBER IN EACH OF SAIDRECIRCULATING ZONES SUBSTANTIALLY TRANSVERSELY THROUGH AND ABOUT SAIDFRESHLY WET SPUN FILAMENTS PASSING THERETHROUGH, AND WITHDRAWING ZONE INSAID WASHED FILAMENTS FROM SAID WITHDRAWING ZONE IN SAID CHAMBER.